The goal of this work is to elucidate the mechanism of action of luteinizing hormone (LH) in stimulating steroidogenesis in the bovine corpus luteum. At this time the work is divided into three major specific aims as follows: 1) To reassess the mediatory role of cyclic AMP in the action of LH. This has been carried out by simultaneously measuring changes in cyclic AMP, protein kinase and steroidogenesis in luteal tissue preparations. 2) To study how LH stimulates the adenylate cyclase enzyme system of this tissue. This is being done by solubilizing and purifying the hormone sensitive adenylate cyclase. At each step in the purification of this enzyme system we hope to study the effect of LH on its activity to gain some insight into the mechanism of activation of the enzyme by LH. 3) To study how cyclic AMP accelerates the steroidogenic pathway. Two approaches are currently under investigation. One is to pursue the investigation of the activation of the cholesterol side-chain cleavage enzyme system by cyclic AMP, and the other to study the possible role of microfilaments in the acceleration of steroidogenesis by LH and cyclic AMP. BIBLIOGRAPHIC REFERENCES: Ling, W.Y., Marsh, J.M., and LeMaire, W.J. "Adenosine 3',5'-monophosphate in the Plasma from Human Pregnancy". J. Clin. Endoc. Metab. 44:514 (1977). Ling, W.Y. and Marsh, J.M. "Reevaluation of the Role of Cyclic Adenosine 3',5'-monophosphate and Protein Kinase in the Stimulation of Steroidogenesis by Luteinizing Hormone in Bovine Corpus Luteum Slices." Endocrinology 100:1571 (1977).